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What Type of Stucco Do I have?

For the homeowner, stucco is a term loosely applied to various kinds of plasterwork, both exterior and interior.  The most common use is to refer to plaster or cement used for the external coating of buildings. Hard Coat Stucco consists of a mixture of cement or lime, sand and water, applied in one or more coats over rough masonry or frame structures. 

Synthetic versions of stucco have come into wide use that include acrylic resins or polymers.  The most common type is known as Barrier EIFS  (Exterior Insulation and Finish System).   EIFS has been used for a little over three decades in the USA.  It was developed in Germany during the 1950's to assist in the re-building of Europe after World War II.  EIFS combines exterior finish system durability with good thermal insulation and a variety of texture color retention.   In the late 1990's EIFS manufacturers started to develop and market a second generation of PB-EIFS for wood frame construction.  These are often generally referred to as Moisture Drainage EIFS or MD PB-EIFS .

Hard Coat Stucco (HCS) has been used for decades, traditionally three coat stucco has a long history that is well accepted and defined in the Model Building Codes.  The newer One-Coat Stuccos (OCS)  are thinner with proprietary mixes that require code body evaluation service reports for local building officials to review and allow use of products in their jurisdiction. 

Traditional Stucco facts:

  • A Moisture Barrier is required on top of moisture sensitive substrates such as wood, gypsum, etc.

  • Three coats or layers with a total thickness of 3/4 of an inch or more - Scratch Coat,  Brown Coat, and Finish Coat.

  • Metal Accessories - Casing Beads or Stops or Grounds, Weep Screeds, Corner Aids, and Control Joints or Expansion joints at 144 square feet.

  • Flashings are required as a part of weatherproofing the system.

  • Vulnerable to excessive cracking.

  • Details are well developed; see Northwest Walls and Ceiling Bureau Stucco Resource Guide.  top

One-Coat-Stucco is a newer stucco system that is very similar to traditional stucco but with some advantages.  It provides design flexibility, durability and water management. It can also  be finished in a variety of ways including premixed colored cement stucco finish coats, elastomeric coatings and paints or even acrylic textured finishes.

Each one-coat stucco system is a proprietary mix of Portland cement, polymers, fiber reinforcement and secret ingredients.  Each approved One-Coat-Stucco has its own Evaluation Report by the various Model Codes (the Model Codes have recently been merged into one Model code, ICC or IRC). Note:   The One-Coat-Stucco name is a misnomer since  there are actually at least two coats.

  •  A Moisture Barrier is required on top of moisture sensitive substrates such as wood, gypsum, etc.

  • One-Coat-Stucco is applied in coats with a total thickness of 3/8 to 1/2 inches - a brown or base coat and a finish coat.

  • Metal Accessories - Casing Beads or Stops or Grounds, Weep Screeds, Corner Aids, and Control Joints and Expansion joints at 144 square feet, window and door corners and per architectural details.

  • Flashings are required as part of weatherproofing the system.

  • Vulnerable to cracking.  Although, if mixed and installed properly, the proprietary mixes are very effective at minimizing cracking.

  • Details are typically well developed and part of the Evaluation Report or the Manufacturer's installation manuals.  See the Northwest Walls and Ceiling Bureau Stucco Resource Guide for further clarification.  top

EIFS (Exterior Insulation and Finish System) or Synthetic Stucco 

Since EIFS is a non-load bearing exterior wall system, the system's primary function  is  to provide a weather barrier, thermal insulation and an attractive exterior cladding.  When properly installed and maintained, the system will provide many years of beauty and function.

The two basic types of EIFS are Barrier EIFS and the newer Moisture Managed EIFS.  Both systems require following the manufacturer's installation details carefully.

Barrier EIFS has been used for over three decades in the USA.  Most EIFS used on residences were PB EIFS (Polymer Based).  Each system is a proprietary mix and has its own Evaluation Report by the various Model Codes (The Model Codes have recently been merged into one Model code, IBC or IRC)

  • System Components:

    • EPS (Expanded Polystyrene) insulation properly attached to substrate or framing.

    • EPS properly prepared to receive basecoat.

    • Polymer Based basecoat applied to EPS.

    • Fiberglass mesh immediately embedded into fresh basecoat.

    • Finish Coat properly applied to cured basecoat.  

  • No PVC or metal Accessories; however, edges must be properly back-wrapped to protect the EPS and minimize damage.

  • Details have developed over the past 30 years by the individual manufacturers and EIMA.  Top

Moisture Drainage EIFS

The newer Exterior Insulation Finish systems, Moisture Drainage EIFS, uses a drainage plane and moisture barrier on top of the moisture sensitive substrates.  Each system is  proprietary and has its own Evaluation Report by the various Model Codes.  As was stated above, the Model Codes have recently been merged into one Model code, IBC or IRC.  A moisture barrier is required on top of moisture sensitive substrates such as wood, gypsum, etc.

Moisture Drainage  EIFS System Components are very similar to Barrier EIFS

  • EPS (Expanded Polystryene) insulation properly attached to substrate or framing.

  • EPS properly prepared to receive basecoat.

  • Polymer Based basecoat applied to EPS.

  • Fiberglass mesh immediately embedded into fresh basecoat.

  • Finish Coat properly applied to cured basecoat.

  • Flashings, at roofs, decks, windows and doors, are required as part of  weatherproofing the system.

  • A sheet or liquid applied moisture barrier.

The significant difference, in addition to the Moisture Barrier, is the use of PVC Accessories.

  • PVC Weep Screeds at bottom of all walls and above windows, doors, decks or doors

  • Horizontal Expansion Joints must allow for the drainage of moisture.

  • Flashings are required as part of  weatherproofing the system.

Properly installed EIFS Moisture Drainage systems should also be resistant to cracking.  The details are typically well developed and part of the Evaluation Report or the Manufacturer's installation manuals.  top